The increasing prevalence of obesity and its co-morbidities and the limited success of previous weight loss/maintenance interventions argues the need for new approaches to prevent obesity. Peri-menopausal women are t high risk to develop overweight and obesity. Around that period, physiological and behavioral factors contribute to changes in energy expenditure which promote energy surfeit and progressive gain of total and abdominal fat, often exacerbated by loss of lean tissue Thus, we propose to develop and test an innovative individualized weight loss/maintenance program for overweight peri-menopausal women, driven by frequent assessment of subjects' biopsychosocial profiles (allowing timely intervention response to individual needs), and delivered through extensive use of new communication technologies (primarily and Internet-CD-ROM hybrid package) which have been largely unexplored in behavioral and biological research. To this end, overweight/obese peri-menopausal (aged 45 to 55 years) women will be randomized to intervention (n=50) or control (n=50) after completing a 3-month core curriculum exercise, diet, and cognitive- behavior therapy. After a 3 months transition with computer training (intervention group only), intervention (15 months) will proceed via the internet only, except for laboratory measurements (intervention and control groups). Increased physical activity (approximately 1500 kcal/week), healthy eating and modest calorie restriction with adequate nutrients will be targeted, with special emphasis on promotion of self-directed behavior. Biopsychosocial "weight loss profiles" will be monitored through questionnaires on the web site and used to individualize intervention, respond to change needs, and assess their relationship with changes in body weight and composition measured by dual energy x-ray absorptiometry. We contend the internet/web site technology represents a potentially low cost and effective means for providing the continuous education, encouragement and social support to foster sustained behavior change and weight loss/maintenance.